Introduction:
Spinal manipulation entails a range of manual maneuvers that stretch, mobilize, or manipulate the spine, paravertebral tissues, and other joints to relieve spinal pain (1). Manipulation of the spine differs from mobilization, as it involves a sudden applied thrust that the patient generally cannot resist. In contrast, mobilization involves a low-velocity, passive movement that can be limited or even halted by the patient (2). Numerous absolute and relative contraindications of spinal manipulative therapy (SMT) have been proposed (3–5). The safety of SMT requires rigorous control. In particular, manipulation of the upper spine has been associated with serious adverse events such as cerebrovascular accidents, paraplegia, rib fractures, and death (6–9). The reported cerebrovascular insults were primarily due to vertebral artery dissection (8). The cervical internal carotid artery (ICA) is less frequently injured during chiropractic maneuvers, probably because it lies in the soft tissue of the neck and is thus more mobile. The ICA has seven segments: cervical, petrous, lacerum, cavernous, clinoid, ophthalmic, and communication (10). The cervical segment begins at the carotid bifurcation) usually at the level of C3(and ends at the skull base and usually has no branches (11). It is assumed that ICA dissection during chiropractic manipulation results from artery compression against either the transverse processes or the bony mass of the upper cervical vertebrae (12). Flexion-extension trauma is more likely to injure the carotid arteries, whereas rotational trauma more often damages the vertebral arteries (13,14). Eagle syndrome was first described in 1937 by the German otorhinolaryngologist Watt Eagle, whose clinical and radiological definition of the condition is still in use. Eagle’s syndrome is a complex symptom assortment produced by provocation of the carotid space structures by anomalies of the styloid process (15), including an elongated styloid of 30 mm or larger (16), insulting angulation, calcification of the stylohyoid or stylomandibular ligaments, and/or approximation of the styloid to C1 transverse process, commonly seen with a styloid of normal length (17). Institutional Review Board approval was waived, and informed consent was obtained from the patient to publish the case details and images.